What would help is if clubs had a clearer idea of their purpose and then advertised that. They need to decide whether their priority is to a paying audience or whether it is to the floorsingers.

If the former, then they should exercise some quality control over which floor singers are invited to perform and ensure that the guest artist, who people have paid to see, gets their full slot.

There's nothing wrong with clubs which choose to prioritise participation and encourage everyone to have a go, provided it is clear that this is what they do, and that from a listener's point of view not to expect very polished performances. Ideally they should encourage people to learn and improve. There is a parallel in the "tunes" world where "slow sessions" have sprung up for musicians who lack the ability or confidence to take part in full-speed sessions.